In the field of display technology, a flat panel display device, such as a Liquid Crystal Display (LCD) and Organic Light Emitting Display (OLED) have an important place in the area of display due to their advantages of light weight, thinness, low power consumption, high brightness, and high picture quality.
In particular, a flat panel display device with high resolution and high picture quality is favored by people. Currently, delay of image signals is one of the key factors that restrict the flat panel display device with high resolution and high picture quality. Specifically, the delay of image signal is mainly determined by the resistance of gates and gate lines on an array substrate and the related capacitance. When opening the gate lines, the corresponding pixels are charged, and some of the pixels are charged insufficiently due to the delay of image signals, which causes the brightness of image display pictures to be nonuniform and badly affects display quality of images. Decreasing resistance of the gates and the gate lines can decrease the delay of image signals, and thus improving picture quality of images.
Currently, a method for decreasing the resistance of the gates and gate lines is: using copper (Cu) which has low resistance to produce the gates and scan lines (those are the gate lines). However, the above-mentioned method has the following disadvantages:
Cu is easy to diffuse and easily diffuses into a gate protection layer, a semiconductor layer, a passivation layer, etc., which seriously affects the performance of a thin film transistor (TFT). In the prior art, when manufacturing a top-gate type TFT, a semiconductor layer is formed firstly, and a insulating barrier layer is deposited before depositing a Cu metal gate and a gate line thin film, so as to prevent the Cu ions from diffusing toward a gate insulating layer and the semiconductor layer, but in a subsequent heating process, the activity of the Cu ions increases, therefore they can still traverse the insulating barrier layer and permeate into the semiconductor layer, and thus seriously impacting the performance of the TFT, making the picture quality of images worse, and even destroying normal operation of the TFT.
A TFT on an existing array substrate and its manufacturing method may cause problems of performance degradation of the TFT and poor picture quality of images.